sedimentary
River Pebble (Siltstone/Mudstone)
Clastic sedimentary rock
AI-generated identification · may be incorrectHardness: 3-5 (Mohs scale), Color: Dark brown to reddish-brown, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: None (conchoidal or irregular fracture), Specific gravity: 2.3-2.6
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Physical properties
Hardness: 3-5 (Mohs scale), Color: Dark brown to reddish-brown, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Cleavage: None (conchoidal or irregular fracture), Specific gravity: 2.3-2.6
Formation & geological history
Formed through the accumulation and compaction of fine-grained clay and silt particles in low-energy aquatic environments such as riverbeds, lakes, or floodplains. This specimen shows significant rounding due to aqueous erosion over long periods.
Uses & applications
Primarily used in landscaping, road construction gravel, or as a substrate in aquariums. These smooth stones are also popular for painting or decor.
Geological facts
The rounded shape is a result of 'saltation' where the rock bounces along a river bottom, chipping away sharp edges. These stones can often contain tiny micro-fossils or organic matter.
Field identification & locations
Identify by its smooth, water-worn texture and fine grain size where individual crystals are not visible to the naked eye. Found worldwide in active or ancient riverbeds and shorelines.
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